A new update is introducing what it calls "contextual reminders". It will remind you when it's worth to read an email. It does it by reading the content of the email and judging when it think it's worth notifying you.
So, for example, if you've got an email about an appointment, it may just pop up a little beforehand to remind you it's coming up.
It seems to be a great little addition to the already impressive email client. But isn't it a serious step into our privacy?